1. Technical Field
The present disclosure relates to capacitors to be used in a variety of electronic devices or in storage battery units for vehicles.
2. Background Art
An electric double layer capacitor makes use of a storage function of an electric double-layer formed on an interface between a polarized electrode and an electrolyte. In general, the electric double layer capacitor includes a pair of polarized electrodes (positive electrode and negative electrode), an electrolyte, a porous separator, a pair of current collectors, and a container accommodating the foregoing structural elements. The pair of polarized electrodes is impregnated with the electrolyte. The separator isolates the pair of polarized electrodes from each other for preventing them from shorting with each other. Current collectors are coupled to the polarized electrodes, respectively.
The electric double layer capacitor discussed above features the following advantages over a secondary battery:                a longer service life, and no replacement needed;        capability of being charged instantaneously; and        capability of discharging a greater amount of electric current.Due to these advantages, the electric double layer capacitor has drawn attention from the market in recent years as a load leveling power supply or a back-up power supply when the electric double layer capacitor is combined with another power supply.        
In order to use the electric double layer capacitor in a high-temperature atmosphere, it has been studied to adopt an electrolyte of being excellent in heat resistance and of generating a smaller amount of gasses. An adoption of an electrolyte containing γ-butyl-lactone or γ-valero-lactone is proposed as an example of the foregoing electrolyte.